Hand tool for bending the edges of sheet-metal parts



March 5, 1957 b c 2,783,668

HAND TOOLFOR BENDING THE EDGES 0F SHEET-METAL PARTS Filed 001; 25, 1950 Zia/gyro: W, F5LICH M l I HAND TOOL FOR BENDING THE EDGES F SHEET-METAL PARTS Max Friilich, Sindelfingen, Germany, assignor to Daimler- Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Application October 25, 1950, Serial No. 191,983

Claims priority, application Germany October 27, 1949 8 Claims. (Cl. 81-15) This invention relates to a power driven hand tool for bending the edges of sheet-metal parts. It is an important object of the invention to provide a simple and light, but nevertheless efficient tool whose driving member is either connected to a remote drive, for example, by means of a flexible shaft, or connected directly to a prime mover, for example, an electric or pneumatic hand drill.

Another object of the invention is to provide a handy bending tool for bending the edges of large, bulky and correspondingly heavy sheet-metal parts which due to their bulk can not be handled anymore on stationary sheet-metal Working machines, by way of' example, such parts as automobile bodies and relatively large component parts of the same.

Accordingly, an important feature of the invention consists therein that the working surfaces of the bending tool, defining a working space outside the body of the tool, are arranged on two levers fulcrumed in the body of the tool which levers, for example, bymeans of cams or eccentrics are brought towards each other in a hammering motion. Depending on the respective cross-sectional form of the sheet-metal edges to be bent and on the direction of the blows dependent thereon, each of the levers carrying the working surfaces can. be constructed as single or double lever. In such a case, andin accordance with another feature of the invention, one of the two levers may be actuated directly by a cam or eccentric arranged on the drive shaft, whereas the second leveris actuated by means of said first lever. .The. directly actuated lever is preferably the respective lever which does the forming of the sheet-metal edge and which for this purpose is provided with a slightly rising working surface so as to give the sheet-metal edge to .be bent a start, whereas the indirectly actuated lever serves preferably and mainly as dolly and guide for the tool, its working surface being of a shape conforming to the desired cross-sectional shape of the finished-bent sheetmetal edge. In order to holdthe sheet to be bent on points adjacent to the edge to be bent, another or additional dolly, coacting with the second lever, may be provided which forms the one end of a third lever, for example, likewise constructed as double lever, or is actuated by the same, whereas the third lever itself receives its actuation, for example, by means of the same cams or eccentrics as both of the other levers.

The accompanying drawing illustrates one embodiment of the invention. In the drawing:

Fig. l is a longitudinal section through the new hand tool,

Fig. 2 is a front view of that which is shown in Fig. 1,

Fig. 2a is a perspective view of the lever which does the bending of the edge and Fig. 3 is a plan view of the hand tool provided by the invention.

The rear wall 8, connecting the two sides 6, 7, of the inverted U-shaped body or frame 5 is provided with a hired States Patent 0 the drive shaft is inserted into the tool.

connecting piece 9 through which drive means such as For. the drive shaft there may be used either a flexible shaft which is driven by an electric motor disposed independently of the hand tool, or the drive shaft of an electric or pneumatic hand drill which'then is rigidly secured to the body 5 of the tool.

The end of the shaft 10 extending into the tool is at 11 once more supported in a cross-member 12 of the'body' and provided with a drive member in the form of adouble cam 13 having risers 13a and 13b by means of which, as the shaft is rotated, three levers 17,18, 19,

Each of the three levers having its particular function and being especially constructed is hereinafter more fully f described.

The lever 17 which actually does the forming properis constructed as a single lever and on its free end 22 provided with a ball bearing 23 whose outer ring 24' is in frictional contact with the cam 13. The lever 17,"

being of angular shape (as seen in side view) has at its apex a protruding working surface 25 whose shape is clearly shown in Fig. 2a, and which is constrained by its position relative to the fulcrum pin 14 to perform a hammering motion in the direction of the arrow 26 whilst the 'bending tool is operated.' Simultaneously with it the working'surface 27 of the lever 18 which is 'pivoted on fulcrum pin 15 performs'a countermovein the direction of the arrow 28, since the lever 18 is constructed as a double lever and supports itself with its end 29 on the end 22 of the lever 17. Theworking'surface 27 has the cross-sectional form of the finished bend 20, a'ccordingly the lever 18servesessentially only as a rhoving dolly which, as comparedto a resting dolly, hasthe advantage that with it one obtains with a relatively light mass as good a countereaction as of considerable weight.

P In operation, the device is slipped onto the'edge 20 of the sheet to be bent in the direction of the arrow 30,

with the level portion"31 of the lever 17 at its leading edge,and advanced inthis direction, thus the sheet-metal edge, positioned in the space between the working surfaces 25' and 27, 27a, is progressively formed by the sloping surface 31 and then receives its final shape by the dimensions exceed the amplitude of the hammer stroke.

For still further improvement of the bending tool so as to render it serviceable for certain classes of work, a guide member 32 is slidably guided in key-ways 33 of the side-pieces 6, 7 of the body of the tool. Its level working or guiding surface 34 performs hammering motions in the direction of the arrow 35 in unison with the working surfaces 25 and 27, and at the same time it cooperates with the portion 27:: of the working surface of the lever 18 in such a manner that the portions of the sheet-metal part 21 situated adjacent to the edge 20 (to be bent) are clamped between the surfaces 34 and 27a and held there so as to obviate any undesirable bending or rebounding of these portions. The hammering motion is imparted to the dolly 32 by the double lever 19, which von its one end carries an adjustment screw'36 and on its other end a ball bearing 37 bearing against the Patented Mai-.5, 1957 v with a resting dolly' cam 13. If opportune, the working surface 34 may also be integral with the lever 19 or with a rigid extension of the same, so that it itself serves as dolly, with suitable modification of the keyways 33, thereby omitting parts 32 and 36.

The return movement of the levers is accomplished by their own weight, however, suitable springs may also be provided for this purpose.

Although in the foregoing description I have described my invention only in connection with the bending of sheet-metal edges I do not wish my invention to be limited or restricted to suchuse or to the details of construction shown, but wish my patent protection to cover the spirit and scope of the invention as defined by the appended claima- What I- claim is:

1.- A- hand tool for bending the edges of sheet metal parts comprising a frame, a rotating drive shaft supported in said frame, a cam wheel on said shaft for converting the rotary movement of saidshaft into a reciprocating movement and having two opposed cam surfaces, a first lever, a second lever, a third lever, means pivotally supporting each said lever in said frame, oscillatory work surfaces on said first and second levers conforming to the desired cross-sectional form of the bend to be produced, said second leverbeing supported against said first lever for actuation thereby, said first and third levers being arranged in the same plane at opposite sides of said drive shaft, one of saidcam surfaces actuating said first lever each time the other cam surface actuates" said third lever, and a guide member for guiding the tool in the plane of the sheet metal part, said guide member being actuated by said third lever with a reciprocating hammering motion in the swinging plane of the levers.

2-. A hand tool for bending the edges of sheet-metal parts comprising a frame, a driving member, a first and a second lever, means supporting said levers in said 'frame' for pivoting movement about parallel axes, means defining enacting working surfaces on said levers eonforming. to the cross-sectional form of the bend to be produced and bounding a space for the sheet metal part outsidevthe frame, and drive means causing said driving member to impart an oscillatory hammering movement to said levers, the driving member and the working" sur-' face ofthe first lever being positioned on a same" side of the pivoting axis ofsaid first lever, and the driving member and the working sun-ace of the second lever beingpositioned on opposite sides of the pivot-ing axis of said second lever.

3'. A hand tool according to claim 2, wherein said first lever is operatively connected directly to saiddriving member and said second lever is connected to said driving member through said first lever.

4. A hand tool according to claim 2, in combination with keyways in said frame extending parallel to the direction of said hammering movement, a guide member slidable in said keyways, means on said guide member defining a guide surface for the sheet-metal part to be bent for guiding the same in its own original plane, and a third lever including means abutting against said guide member and means causing said drive member to impart an oscillatory hammering movement to said third lever in a direction perpendicular to said plane and a corresponding movement to said guide member.

5. A hand tool for bending the edges of sheet-metal parts comprising a frame, a driving member, a first, a second and a third lever, means supporting said levers in said frame for pivoting movement about parallel axes, means defining respectively concave and convex coacting working surfaces on said first and second levers conforming to the cross-sectional form of the bend to be produced, and bounding a space for the sheet metal part outside the frame, and a guide surface for the sheet-metal part to be bent movable with said third lever, and drive means causing said driving member to impart an oscillatory hammering movement to said three levers with said guide surface extending in a plane perpendicular to the planes of oscillation of said levers and substantially parallel to the original plane of the sheet-metal part to be bent.

6; A handtool according to claim 5, said levers being all three actuatedsimultaneously by said drive member to performa working stroke towards the sheet-metal part.

7. A hand tool according to claim 2, said frame havinga U-shaped cross-sectional form with two side pieces, said levers beingsupported on pivot pins extending transver'sely between said side pieces,- and said working surfaces defining therebetween a working space for the sheetmetal part positioned externally of saidside pieces.

8. A hand tool according to claim 4, said'frame hav ing a U-shaped cross-sectional form with two side pieces, said lever-s being supported on pivot pins extending transversel-y between said side pieces, said keyways being provided in said side pieces and having end faces form'- ing" a oontinuation of said guide surface on either side thereof for additional support for the sheet metal part.

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